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Use 14 gauge single conductor for your common wire, and you can get by with 18 gauge multi-conductor for the zone valves. This will even work for older valves with higher current draw. (modern valves might get by with all 18 gauge) Do yourself a giant favor and try to limit the distance between valve boxes to 100 feet. This is because expansion and (especially) contraction may strain the wire. An 'expansion coil' can be made by winding a couple feet of wire around a small pipe.

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Wet_Boots</i>
<br />Use 14 gauge single conductor for your common wire, and you can get by with 18 gauge multi-conductor for the zone valves. This will even work for older valves with higher current draw. (modern valves might get by with all 18 gauge) Do yourself a giant favor and try to limit the distance between valve boxes to 100 feet.http://edis.ifas.ufl.edu/images/1461946812

Thanks - that takes a load off my mind because I can get those wires readily and you have saved me a lot of money by going with the smaller gauge. <b>Plus</b> the 18 gauge comes in multi- which will add flexibility to what I am trying to do. (None of the valves are planned. I just want to get as much as possible in the ground while it is trenched.)

I am however worried now about expansion. My plan was to drop the wire into the ground and there will be hundreds of feet between valve boxes. I wonder if I should just go ahead and place some expansion coils right in the ground about 100 feet apart. Possibly just creating a coil as you show there inside a small section of my 2" PVC pipe. Or some other protected covering.

I would put in expansion coils every 100 feet or so, this way, reguardless of where you place your valves, you should be alright. Ideally, you want the expansion coil at the valve, but if you are unsure of where you are placing your valves, go for the next best thing. Like Wetboots said, if you are using modern valves, 18 GA wire all around will be just fine.

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by RidgeRun05</i>
<br />I would put in expansion coils every 100 feet or so, this way, reguardless of where you place your valves, you should be alright. Ideally, you want the expansion coil at the valve, but if you are unsure of where you are placing your valves, go for the next best thing. Like Wetboots said, if you are using modern valves, 18 GA wire all around will be just fine.
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Thank you, but I might have interpreted this wrong.

I was thinking that the expansion coils were needed for soil movement. And in my mind I could envision that as a very likely possibility for various reasons. But maybe I took this wrong. Maybe you are talking about some kind of expansion that happens right at the valve.

In either case I will install coils every 100 feet or so even if underground. it still makes sense to me that the ground could move and place stress on the wires - possibly breaking them underground if the movement was severe enough.

It also looks like most installations go with uncut wire. My runs are so long that I do not know if I have that luxury.

Is this an absolute rule that the wires are not spliced together? If I am forced to do splices, can I get by OK with soldered connections at the splice?

You want to make as few splices as possible, but if it is absolutely unavoidable, a soldered connection would be better than just grease caps alone. You are correct, you want the expansion coils installed to that if the wire moves at all, it has room to shift. You just don't want the wire tight. It really doesn't matter where you put them. You do want to pig tail the wire at the valve though as well, so you have some wire to work with.

I would advise against any soldered joints underground in a sprinkler system. Not that it can't be done. It is just possible, however, to do it wrong, and get a 'time-bomb' electrical fault. Little round valve boxes are cheap enough to use one at every wire junction, so you have access to every mechanical wire connection.

And yes, you can wind expansion coils and place them inside a larger diameter pipe, where they can move freely. Working with open trenches allows you to do this.

Could you place all the valves on one location and run the mains to the various zones. Example; I am looking at a 9 zone install with various types of watering heads. I was thinking that I could build central valve box with main distributed to the various locations. This way I can maintain the valve units in one location, place a backflow valve in this cintral location, and implement a fertalizer infrastructure all in one place, up close to the house without having valve boxes distributed throug the lawn. What is the best way to approach valve placement?